Gravelless septic drainfield site requirements:

This article explains the site requirements, design criteria, and construction details of a gravelless or "no gravel" or "no rock" septic drainfield systems, offering installation specifications.

Citation of this article by reference to this website and brief quotation for the sole purpose of review are permitted. Use of this information at other websites, in books or pamphlets for sale is reserved to the author. Technical review by industry experts has been performed and comments from readers are welcomed. Contributors are listed at the end of each article.

Site Requirements & Design Criteria for Gravelless Septic Absorption Systems

Drainfields, also called leach fields, absorption beds, soil absorption systems, and leaching beds, perform the functions of septic effluent treatment and disposal in onsite wastewater treatment systems, conventionally called "septic systems".

Typical gravelless septic systems use a plastic chamber, a geotextile-wrapped pipe, or a polystyrene-wrapped pipe to distribute effluent into the soil.

The necessary soil absorption area is provided by the perforated surface of the gravelless septic system components (or by soil at the bottom of a chamber) themselves rather than by the gravel and trench walls of a conventional septic drainfield.

Site Requirements for no-rock chamber or textile wrapped septic effluent disposal systems:

These systems shall be used on sites that have been classified as having a design percolation rate of one to 45 minutes per inch, and meet the vertical and horizontal separation distances in Table 2 (of the New York State Standard - for example) shown

in 75-A.4 Soil and site appraisal for Septic Systems.(2)

Chamber systems provided by Infiltrator Inc. (links below) have been approved for use in some states, including New York, at perc rates up to 60 minutes/inch, and in some other states, at percs up to 120 minutes/inch. Approval letters are available from that company.

Design criteria for no-rock chamber or textile wrapped septic effluent disposal systems:

The local health department having jurisdiction shall be contacted prior to construction regarding the acceptability of specific products for use as a gravelless distribution system. (3)

As we described above when discussing Geotextile-Wrapped Perforated Pipe systems for onsite wastewater treatment and disposal, the total lot area in square feet which is required for a given alternative treatment system will vary not only depending on the anticipated daily flow, flow rates, soil and site conditions, but also on what spacing requirements the local or state code officials will require.

So although a number of alternative treatment systems including these gravelless methods are capable of working in a smaller total square foot area than a conventional drain field, depending on what the local authorities require in spacing, more area may be required than the minimum.

For example, many states require that space be set aside to allow for future absorption line replacement in between the planned lines.

Construction Specifications for gravelless septic absorption systems

Gravelless distribution systems shall be installed in conformance with the manufacturer's instructions because of the proprietary design of some products.(4) The length, width, and depth of the required excavation will vary by individual product.

The essential difference between a gravelless wastewater treatment system and a conventional perforated-pipe and gravel-trench drainfield is the use of a special product to distribute and release effluent (sketches above) and the absence of gravel in the trench where the distribution system is buried.

The special gravelless products used are designed to avoid soil-clogging right at their surface or they would have a short life.

This concern is addressed by use of special materials (such as geotextiles) which resist soil clogging, and by a design that provides an adequate total area in square feet for soil contact.

Each product manufacturer should be expected to provide an installation manual for the product that you are going to use. The list below is generic and incomplete as site specific and product specific details can't be provided here.

• Perform a site survey to determine the size, layout, and materials needed. The manufacturer indicate the disposal area provided by the product (per linear foot, for example) but your engineer and installer need to evaluate your soils and daily wastewater usage to determine the amount of leaching area needed for your site.
• Tables of field sizing and soil percolation test procedures are provided
  
  at THE SEPTIC SYSTEMS WEBSITE.
• Obtain local building code or board of health requirements
• As with any wastewater disposal field, never drive equipment in or over the trenches. Compacting the soil (or after installation, damaging the drainage components) will reduce the absorption system capacity or may destroy it completely.
  
  Some systems such as Infiltrator Inc. chambers, have been tested to meet an H-10 engineering rating (16,000 lbs / axle), so occasionally if a system built using some chamber products are driven over it won't necessarily be an issue. But Infiltrator Inc. 's technical experts do not recommend constant vehicle traffic over anything but their heavier duty H-20 chambers.
  
  These disclaimers notwithstanding, it remains a better practice to keep all traffic off of septic fields. And even where septic equipment has been described as rated for vehicle traffic, heavy equipment traffic can cause some surprising collapses that can be costly to repair as shown in THIS PHOTO.
• Some sites may need a curtain drain or other special measures to redirect surface or subsurface runoff away from the effluent/wastewater absorption area.

Chamber Septic - No-Rock Septic Design Critera, Guides, Specifications

• Also see more product specifications and design guides
  
  at GRAVELLESS NO-ROCK SEPTIC SUPPLIERS
• ADS ON SITE SEPTIC SYSTEMS PRODUCT DESCRIPTIONS [PDF] retrieved 2019/02/11 original source: http://www.pmstp.com/img/pdf/en/10265_On-Site_Septic.pdf
  
  ADS - ARC 18-24 LEACHFIELD INSTALLATION GUIDE [PDF] for ADS ARC 24 leach field Chambers
• CPP’S No-Rock ™ Fabric Wrapped Septic Pipe [PDF] (2019) Crumpler Plastic Pipe, .O. Box 2068, Highway 24 West, Roseboro, NC 28382 USA, Tel: 1-800-334-5071
  Email: cppsales@cpp-pipe.com retrieved 2019/02/11 original source: www.cpp-pipe.com/no_rock.html
• Hancor Technology, INSTALLATION GUIDELINES FOR GRAVELLESS PIPE FOR SEPTIC TANK LEACH FIELDS [PDF] (20056), Hancor Technology, Website: http://www.hancor.com/product/Gravelless_Septic_Design.html Tel: 888-FOR-PIPE
  retrieved 2019/02/11 original source: https://www.lawsupply.net/storm_drains/Hancor/gravelless_pipe_install.pdf
  
  Excerpt: As an alternative to gravel filled soil absorption trenches for septic tanks, the Hancor Gravelless Pipe system is recommended.
  
  Corrugated high density polyethylene pipe is factory inserted in a synthetic filter material of Cerex® Type 25 protective wrap. It is available in both 8” and 10” diameters (inside) and in standard 20’ lengths.
• Hanson, Adrian, Ph.D., P.E., Craig Runyan, Bruce Lesikar, A HOMEOWNERS GUIDE: INSTALLING A SEPTIC TANK AND DRAINFIELD [PDF] (2006), New Mexico Environment Department, Tel: 1-800-219-6157, retrieved 2019/02/11 original source: https://www.env.nm.gov/wp-content/uploads/2017/08/Homeowner-Notebook-final-2006.pdf
  
  This guidance is restricted to the Homeowner installing a conventional septic tank and drainfield system for their primary residence. It is also restricted to system receiving less than 2000 gallons/day and no more than 500 gallon/day/acre of liquid waste. Includes details on installing or constructing a gravelless septic system.
  
  Includes construction details for gravelless septic systems.
• Hygnstrom, Jan R., Sharon O. Skipton, Wayne E. Woldt, RESIDENTIAL ONSITE WASTEWATER TREATMENT: GRAVELLESS DRAINFIELDS FOR EFFLUENT TREATMENT [PDF] (2008) University of Nebraska Extension,
  Excerpt:
  
  This publication explains how gravelless drainfields work and gives drainfield sizing and installation information for a home. It is not intended to provide all information needed to design a gravelless drainfield for a particular site or situation or to guarantee compliance with Nebraska regulations.
  
  Includes formula to convert required conventional drainfield size in square feet of trench area to length of trenches required when using a gravelless pipe.
  
  Basic formula:
  
  Liner Feet of Gravelless Drainfield Trench = [Sq.Ft. Required Standard Drainfield Area] / (0.75 x pipe diameter in ft x 3.14]

• Infiltrator Systems, Inc. provides chamber products and geotextile septic products: Tel: 800-718-2754 Old Saybrook CT USA. Website: http://www.infiltratorsystems.com/ or 4 Business Park Road P.O. Box 768 Old Saybrook, CT 06475
  860-577-7000 - 1-800-221-4436
  
  Infiltrator Systems ARC 18, ARC 24 GRAVELLESS CHAMBER SYSTEM INSTALLATION GUIDE [PDF] Op. Cit.
  
  Infiltrator Systems ARC 36, ARC 36LP, ARC 36 GRAVELLESS CHAMBER SEPTIC SYSTEM INSTALLATION GUIDE [PDF] Op. Cit.
• Oregon, DESIGN AND INSTALLATION MANUAL FOR INFILTRATOR QUICK4 CHAMBERS IN OREGON [PDF] (2016), retrieved 2019/02/11 original source: https://www.oregon.gov/deq/FilterDocs/infiltrator.pdf
  
  For more detailed design information, please contact Infiltrator Water Technologies at 1-800-221-4436
• NESC: GRAVELLESS SEPTIC DESIGN [PDF] Pipeline, NESC, National Envirobnmental Services Center,Box 6893, West Virginia University Morgantown, WV 26506-6893 USA, Email: info@mail.nesc.wvu.edu Tel: (304) 293-4191 retrieved 2019/02/11 original source: http://www.nesc.wvu.edu/pdf/WW/publications/pipline/PL_SU01.pdf copy on file as Gravelless-septic-deisign-NESC.pdf
• US EPA, DECENTRALIZED SYSTEMS TECHNOLOGY FACT SHEET SEPTIC TANK LEACHING CHAMBER [PDF] (2000) Municipal Technology Branch U.S. EPA Mail Code 4204 1200 Pennsylvania Avenue, NW Washington, D.C. 20460 USA retrieved 2019/02/11 original source: https://www.epa.gov/sites/production/files/2015-06/documents/septic_tank_leaching_chamber.pdf
  
  Excerpt: A leaching chamber is a wastewater treatment system consisting of trenches or beds, together with one or more distribution pipes or open-bottomed plastic chambers, installed in appropriate soils.
  
  These chambers receive wastewater flow from a septic tank or other treatment device and transmit it into soil for final treatment and disposal.
• WA DOH GRAVELLESS EFFLUENT DISTRIBUTION PRODUCTS [PDF] (2013) Recommended Standards and Guidance for Performance, Application, Design, and Operation & Maintenance, Washington State DOH, Wastewater Management Section, Post Office Box 47824 Olympia, Washington 98504-7824 USA, Tel: 360.236.3330 FAX: 360.236.2257 Email: wastewatermgmt@doh.wa.gov retrieved 2019/02/11 original source: https://www.doh.wa.gov/Portals/1/Documents/Pubs/337-005.pdf

Consultants or suppliers in this field can be listed at our alternative septic designers page at no charge by contacting me.

Gravelless Septic Design using Poly-Wrapped Pipe

While polyethylene wrapped or peforated-plastic-wrapped plastic pipe is discussed in older no-rock septic system design manuals, the use of poly-wrapped pipe for gravel-less septic effluent disposal has, in our OPINION, been eclipsed by the use of geotextile-wrapped pipe instead.

As of May 2020 it was difficult to even find a vendor selling this product type.

Please see NO-ROCK SEPTIC GEOTEXTILE-WRAPPED PIPE

InspectApedia.com has no financial or other relationship with any suppliers listed at our website and we do not endorse specific products. No fees or costs are involved in product source listings. CONTACT us to add information.

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

Does a Gravelless septic system allow for a smaller drainfield than conventional septic designs?

I was under the impression that a gravelless system allows you to reduce the sq footage of your leach field from a conventional system. My calculations show almost 25% larger sq footage of the total drain field. Ronald Shull · Feb 3, 2022

Reply by (mod) - possibly true - depends on soil properties

@Ronald Shull,

The claimed advantages or cost savings of on-rock systems are given in the article above, but I agree that for a given wastewater effluent daily volume the total space needed for a gravelless septic drainfield will vary depending on the properties of the soil and other site features.

How many ADS ARC 24 leachfield chambers do I need for my no-rock septic system?

I have a 500 gal dome septic tank and I want to use the ADS ARC 24 leach field Chambers for a 2 bedroom, 1 bathroom mobile home.There will be no traffic going across it.

My questions is about how many leach field Chambers would I need?

Will I need 2 end caps? And what type pipes do I buy to run from the house, to the septic tank, to the leach field Chambers? Please help. On 2019-03-21 by Lisa

Reply by (mod) -

Lisa

Please see the gravelless septic design specifications

at GRAVELESS SEPTIC DESIGN CRITERIA above on this page, as that's more complete than an off-the-cuff reply.

But generally, yes you need end caps on each chamber section. The absence of traffic over the drainfield won't changee that requirement.

More gravelless or chamber septic articles that can be useful to you are in the ARTICLE INDEX found above on this page.

A typical gravelless septic design guide from (ADS-ARC) and that applies to your planned septic chamber system can be downloaded as a free PDF at

ADS - ARC 18-24 LEACHFIELD INSTALLATION GUIDE [PDF] for ADS ARC 24 leach field Chambers

For a 450 sqft leach field how many 22" infiltrator connections would I need?

For a 450sqt leach field how many 22" infiltrator connections would I need? On 2019-10-23 8 by Hugh

Reply by (mod) -

Hugh

The answer depends on the number of connections which, of course, for any of these designs, depends on the number of lines to be laid out.

Take a look at

Infiltrator Systems ARC 36, ARC 36LP, ARC 36 GRAVELLESS CHAMBER SEPTIC SYSTEM INSTALLATION GUIDE [PDF]

There you will find that the "right answer" to how many Infiltrator septic system connections are needed will get a bit more detailed: it will also depend on the Infiltrator septic system product that you select.

Infiltrator Systems, Inc.provides chamber products TEl: 800-718-2754 Old Saybrook CT USA. Website: http://www.infiltratorsystems.com/

Infiltrator Systems provides state specific design manuals for no-rock chamber systems for specific states in the U.S.

Example: An Infiltrator Quick4 high capacity 14" chamber system is 34"W x 53"L x 14"H (I didn't find a 22-inch product so perhaps you can point me to the manufacturer and product specifications for the brand and model you're actually considering).

These chamber septics give an actual physical length and an "equivalent" length (as if it were a conventional drainfield trench). The "Effective length" of the model I cited above is 48" - but that does NOT speak to number of connections and thus we need to take care not to mix these two length descriptions.

If you really need 450 sq.ft. of infiltration area for your septic you consider only the length and width of the trench or product.

E.g. 34"W x 53"L x 14"H translates to 34"W x 53"L or 1,802 sq.in. pe chamber section.

Your 450 sq.ft. specification = 450 sqft x 144 (sq. in. in a sq. ft) = 64,800 sq.in.

64,800 total sq. in. / 1802 sq. in. per section = 40 chambers. You need connectors + end caps depending on the number of rows in which your chambers will be connected. That's 38 connectors + 2 ends at the very least, probably more depending on the actual arrangement.

Watch out: all of this is theoretical arm-waving and is NOT site-specific. The good news is if you call the actual company whose product you're buying they'll be thrilled to do the actual calculations for you for their product.

And all of that assumes your local septic engineer has already done a soil perc test and site survey and has told you that 450 is the right sqft. of drainfield chamber bottom area you need.

I Want to install a "no-rock" septic system B101 - are these specs OK?

I am replacing my old septic system with the new system B101 diffusers that do not use rock.

My question is this i was thinking to have 3 drain chanel of 40 feets each is it ok good for my house of 3 bed room and i leave in florida and how deep it have to be thanks in advance On 2019-02-24 by gaston

Reply by (mod) -

Gaston

Take a look at the chamber or gravelless septic system designs and specifications found at

GRAVELLESS SEPTIC SYSTEMS

You'll see that generally you need more space than a traditional drainfield, and that there is ABSOLUTELY no single "right" answer to your it depends on the properties of the soil where your drainfield will be placed, particularly the soil percolation rate.

...

Continue reading  at NO ROCK SEPTIC SYSTEM LIFE or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

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Questions & answers or comments about gravelless or no-rock or chamber type septic absorption field site requirements.